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Home , East Madagascar Current, Mascarene Plateau, Rodrigues, Saya de Malha Bank

9 Deep sea and Offshore/Pelagic Habitats

David Obura

Opposite page: Larval squid in the plankton of the WIO. © Cedric Guiguand/Emmanuel G. Reynaud.

INTRODUCTION • split from and moved northwards, leaving behind a fragment which is now the North Sey- The deep sea habitats of the Western (WIO) chelles Bank 80 mya. are very poorly known, particularly from the perspective of the governments in the region, which have limited capacity The WIO floor is composed of two major plates, the to engage in deep sea research or plan for exploitation of African and Indian plates; the Australian plate lies to the resources in this environment in the near future. Neverthe- east, the Arabian plate to the north. The ocean floor is still less, there are some emerging exceptions to this which will tectonically active, with a spreading rift along the South be presented in this chapter. In view of the paucity of general West and Central Indian Ocean ridges, and northwards in knowledge on deep sea habitats in the region, this introduc- the Carlsberg ridge that extends into the . This tion includes information on their basic structure, followed in continuous ridge system forms the approximate eastern later sections by a summary of their status, knowledge on boundary of the WIO and the African coastline defines the their , and pressures/trends in the future. western boundary (ASCLME/SWIOFP 2012a, ASCLME/ SWIOFP 2012b, Figure 9.1). Plate tectonics The WIO contains both active and fossil tectonic plate Hotspots and other geological features margins, some of the deepest fracture zones in the , Within its broader tectonic margins, the WIO contains a the most complex mid-ocean ridge configurations and number of active hotspots, two of which are of global sig- some of the thickest sedimentary sequences in the world’s nificance and scale. The Mascarene-Reunion ocean basins. The continental land mass of Africa, Mada- became active at the -Tertiary (K-T) boundary gascar, and the North Bank are remnants of the about 67-64 mya, through a massive eruption of magma , which dates from pre-Cam- that formed the in India (classified as a Large brian times over 650 million years ago (mya), and that Igneous Province, or LIP). As the Indian plate moved started to break up 180 mya. Key events include: northwards over the hotspot, a series of island chains were • Formation of the Channel, from about formed: – (57-60 mya), the Chagos 180 -150 mya when Madagascar, , India and Ant- Archipelago (48 mya), Saya de Malha (45 mya), Nazareth arctica rifted from the African coast. and Cargados Carajos (34 mya), (7-8 mya) and • Australia- started to separate from Mada- Reunion (0-2 mya). Only the youngest two, Mauritius and gascar-India 120 mya. Reunion have volcanic features breaking the surface (the

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Figure 9.1. Deep sea features of the Western Indian Ocean, including principal basins and currents Bathymetry is shown at 100 m depth (light blue shading) then at 500 m and 500 m intervals thereafter. Abbreviations: AC , EACC East Africa Coastal Current, EMC East , MCE/CG Mozambique Channel Eddies/ Gyre, SC , SEC .

latter is still volcanically active today); all the others have Ocean basins sunken below the ocean surface and are capped by bio- As a result of these various geological features, the WIO is genic carbonate platforms and coral or islands. The split into four deep basins: the Madagascar (5 500 m, south- Central Indian Ocean ridge itself moved over the hotspot east of Madagascar), Mascarene (4 900 m, west of the Mas- about 45 mya, separating the Chagos and Saya de Malha carene Plateau), Mozambique (5 000 m, south of the Banks. During the Cretaceous, the of Mozambique Channel) and Somali Basins (5 100 m, Madagascar lay over the Marion hotspot, creating a subma- between and the Seychelles, Figure 9.1). Little rine Plateau which extends southwards some 1 300 km at work has been done on the abyssal plains and soft sedi- depths of 1 000-2 000 m, rising above the deeper basins to ments of these basins, though drilling on and near the Mas- the east and west up to 5 000 m deep. carene Plateau shows thick accumulations of marine Seamounts in the WIO are concentrated on the mid- sediments, and terrestrial sediments in the Mozambique ocean ridges, particularly the South West Indian Ridge, Channel, probably washed off the African and Madagascan and scattered around the . Approxi- landmasses by large rivers over >100 million years. mately 700 seamounts have been identified in the WIO region from global studies of bathymetry ASCLME/SWI- Oceanography OFP 2012a, ASCLME/SWIOFP 2012b). Most seamounts The oceanography of the Western Indian Ocean is deter- in the WIO are outside national jurisdiction, with only mined by interactions between the geological features out- those scattered around the Mascarene Plateau being within lined above with the equatorial and western boundary the EEZs of the regional countries. A complex geological currents of the ocean basin. The South Equatorial Current history is suggested by the multiple islands and island (SEC) enters the WIO as a broad slow surface current groups within the Seychelles-Mascarene region (eg Aldabra stretching from about 5-16°S, fed from the Indonesian group, Farquhar/Providence and the Amirantes). Other Through-Flow with waters from the Pacific Ocean, and volcanic features include the island of and passing the at its northern edge. At the Soudan Bank, seamounts in the Seychelles that break the Mascarene Plateau, the SEC is partially blocked, with 50 surface as coral reefs, the Comoros Archipelago, the Iles per cent of its flow forced through the narrow gap between Eparses, and the Davies Ridge in the Mozambique Chan- the Saya de Malha and Nazareth Banks at about 12°S, the nel. remainder flowing both north and south of these two banks.

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Approaching Madagascar, the main flow of the current is at that returns water from the East African coast towards the about 17°S. The banks and island systems lying in the Seychelles, at about 0-2°S. The Asian landmass thus drives pathway of the SEC function as stepping stones for species the seasonal system that dominates climate in crossing the Indian Ocean, providing genetic connectivity. the central and northern parts of the region. Seasonality in Interestingly, there is evidence pointing to west-east trans- the NECC contributes to west-east connectivity that port (Sheppard and others, 2012) as well as in the expected apparently passes through the Chagos/Maldives/Lakshad- east-west direction. weep systems, returning genetic material to the Eastern The tip of Madagascar and the Comoros-Glorieuses Indian Ocean. chain interact with the flow of the SEC and open ocean features such as Rossby waves to generate unique and Productivity highly dynamic meso-scale eddies within the northern Biological diversity patterns in the WIO are driven by the Mozambique Channel. The “Glorioso Front” probably geological and oceanographic features described above. marks the transition from the SEC to the waters of the Interactions between water flow and shallow or deep channel, where a series of clockwise and anti-clockwise bathymetric features can result in strong downstream eddies and an intermittent gyre around the Comoros chain dynamics as a result of eddies (mixing and turbulence) are induced (Ternon and others, 2014). Being driven by induced in the wake of the features, with raised productiv- these features, water may flow in any direction, resulting in ity resulting from this and from the addition of nutrients a highly mixed and dynamic water body in the northern and minerals to otherwise oligotrophic and mineral-poor part of the channel. As the channel narrows at about 17°S, oceanic waters. Closed circulation cells may also form the flow becomes more southward just offshore of the around seamounts, inducing upwelling, trapping nutrients Mozambique coast. Complex forcing of biological parame- and enhancing primary productivity (Harris 2011, Keating ters results from these dynamics, including up- and down- and others, 1987). welling in the eddies and their interactions with the The seasonal dynamics of the Somali Current strongly continental shelves and slopes below at least 1 000 m influence productivity in the northern part of the WIO depth. As a result, the Mozambique Channel is one of the (Schott and McCreary 2001), with strong upwelling in May most energetic western boundary zones of all the world’s to September along certain parts of the coast due to the oceans (Ternon and others, 2014). northward-flowing East African Coastal Current. The sea- The rapid flow of the East Madagascar Current inter- sonal upwelling shuts down during the northeast monsoon acts with the Madagascar Plateau, which extends south- in December to April, but complex currents redistribute wards over 1 000 km at depths of 1 000 to 2 000 m, as it biological production from the upwelling events through- curls around the southern tip of Madagascar. This results out the northern Indian Ocean. in highly dynamic nearshore eddies and nearshore–off- Upwelling in the open ocean between 5-10°S in the shore upwelling over 100s of square kilometres of sea, Central and Western Indian Ocean is indicated by meso- enriching highly productive food webs. This also results zooplankton and biochemistry (Murtugudde and others, in unique communities and high levels of endemicity at 1999) but, although there is some evidence for topographi- the transition zone between the tropical and subtropical cally-induced upwelling on the lee side of the Mascarene regions. These waters merge with waters from the Plateau, this is highly variable and has not been consist- Mozambique Channel and feed into the Agulhas Current, ently or conclusively established (Gallienne and Smythe one of the fastest and narrowest coastal boundary currents 2003). Preliminary results from an ASCLME cruise in 2008 in the world. Most of the Agulhas waters turn 180° (retro- revealed no indication of upwelling, nutrient enrichment flect) and return to the southern part of the WIO at about or enhanced primary production along the leeward edge of 40°S. the plateau (Stromme and others, 2008). In the north, the seasonally reversing Somali Current However, the influence of oceanographic variability and seasonal northern Indian are dominated by and energetics on productivity in the Mozambique Chan- the influence of the Asian land mass and the , nel is emerging (Ternon and others, 2014). Productivity resulting in a highly dynamic system of currents and an is influenced by the direction of flow in the eddies. intermittent North Equatorial Counter Current (NECC) Clockwise (cyclonic) eddies cause upwelling in their

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centre of the , thus raising the thermocline and Marine mammals nutricline closer to stronger sunlight near the surface, A variety of marine mammals frequent the open seas of the resulting in greater productivity in the core of the eddy. WIO, though little work has distinguished between those Conversely, counter-clockwise (anticyclonic) eddies that are open oceanic or pelagic from those found in depress the thermocline and nutricline, resulting in nearshore waters. Many of the large whales frequent both, reduced productivity in the core. However, eddies fre- though they probably spend the larger part of their time in quently interact, particularly when a clockwise and anti- open ocean waters. Beaked whales are more often restricted clockwise eddy are stably adjoined (called a dipole), to open ocean and deep waters, but little is known of their raising productivity in the boundary between them. ecology in the WIO. For example, there are a number of Finally, when eddies (singly or in a dipole) touch the anecdotal records of sightings of colder water species in the continental slope - which may occur frequently as the WIO, including True’s beaked whale (Mesoplodon mirus), eddies may extend over 2 000 m deep - they strip nutri- Shepherd’s beaked whale (Tasmacetus shepherdi), and the ents off the continental slope and make them available to ginkgo-toothed beaked whale (Mesoplodon ginkgodens). pelagic ecosystems. As a result, the productivity of the Recent surveys of islands in the WIO have contributed sig- Mozambique Channel is uniquely high. nificantly to distribution records of marine mammals in the WIO (REMMOA 2012) SCALE OF BIOLOGICAL DIVERSITY (MAIN GRADIENTS OF DIVERSITY FOR SPECIES Marine turtles AND COMMUNITIES) Marine turtles migrate thoughout the WIO, which hosts five species of sea turtle. They are well known from inshore The open ocean and deep sea biota of the WIO are poorly waters due to their need to nest on beaches, resulting in known. Richmond (2001) compiled an inventory of species their vulnerability to hunting and disturbance on popu- identified in the WIO from available records, totalling 10 lated shorelines. Recent tagging studies focused around 627 species in the littoral and shallow subtidal zones. Grif- the and Mozambique Channel have fiths (2005) updated this number to 11 257 through the shown their extensive migrations in all directions (Bourjea Census of Marine Life, claiming this is probably half the 2007) across open ocean areas. actual number. Wafar and others (2011) also commented on the lack of biodiversity information for the region. Work in Seabirds deeper habitats has resulted in the identification of new Eleven seabird families occur within the WIO as breed- species (eg Randall and King 2009). ing species, and fall in three broad categories - Indo- New surveys are revealing previously unknown hot- Pacific or pan-tropical, highly migratory species from spots of biological diversity for benthic invertebrates southern latitudes, and predominantly Atlantic species. (Bouchet 2012), such as the subtropical-temperate south- Though levels of endemism are expectedly low, there are ern coastline of Madagascar. It is likely that deeper at least nine extant, breeding endemics of which five are regions, such as the Madagascar Plateau, will manifest listed as globally threatened, including two critically even greater levels of endemism with previously unde- endangered species (BirdLife International 2012). Half of scribed diversity. Significant investment by the GEF in these are from Sub-Antarctic islands, two from Reunion regional marine assessments over the last 5-10 years, par- Island and two from the Arabian seas. Some of the species ticularly through the ASCLME and SWIOFP pro- found in the WIO are in globally important numbers: eg grammes, has yielded new data in a number of areas 25 per cent of the world’s Sooty Terns Sterna fuscata are (ASCLME/SWIOFP 2012a, ASCLME/SWIOFP 2012b). found on Juan de Nova island, Cosmoledo , Bird The surveys run by SWIOFP and ASCLME covered a Island and Europa Island (Le Corre and Jaquemet 2005, range of topics, including physicochemical conditions, ASCLME/SWIOFP 2012a, ASCLME/SWIOFP 2012b); plankton sampling, soft-bottom meiofauna, trawl sam- >10 per cent of the world’s Tropical Shearwaters (Puffinus ples, acoustic biomass estimates and megafauna observa- bailloni) and Lesser Noddies (Anous tenuirostris) occur on tions; the sections below summarise information in the Aride Island, Seychelles (Fishpool and Evans 2001); and TDA. Aldabra Atoll has the world’s second-largest frigatebird

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colony and is the only oceanic breeding site for the Cas- there would probably be significant gaps. Notably, the pian Tern Sterna caspia (Fishpool and Evans 2001). All of coelacanth Latimeria chalumnae was first found live in the these critical seabird nesting habitats are found in just WIO (Box 9.1) and, though originally thought to be three countries of the WIO - the French islands, Sey- restricted to a few sites in and the Comoros, chelles and South Africa (other subtropical or temperate it is now known to be widespread on continental rises species). throughout the Mozambique Channel and up the East As with marine turtles, while seabirds nest on land African coast to . It may be no coincidence that the and rocks within the coastal zone, their migratory routes age and stability of this continental margin, going back and often their most important feeding grounds are in 180 million years, and the deeply cut canyons that are the open ocean areas. Tropical seabirds associate very coelacanth’s home, have probably been stable throughout strongly with tuna and feed in association with them this time, even with sea level fluctuations. This might be (Le Corre and others, 2012). Thus, their post-breeding the reason for persistence of this ‘living fossil’ here, as it dispersal is probably linked to broad-scale oceanic fea- has gone locally extinct from continental slope habitats tures (such as upwelling or mixing areas) to which fish elsewhere. are attracted. Recent tracking has identified five large- scale Important Bird Areas (IBAs) in the WIO, all in the PROPORTION OF MAJOR GROUPS OF SPECIES open sea (Le Corre and others, 2012): 1) the Seychelles THAT ARE ASSESSED ON A SYSTEMATIC BASIS basin (east of the granitic Seychelles); 2) the pelagic FOR STATUS waters encompassing the Aldabra Group northwards and west of the Seychelles Basin; 3) from Reunion There is insufficient information for oceanic and deep sea southwards; 4) the area south of Madagascar and 5) the habitats to estimate the proportion of groups that have southern third of the Mozambique Channel and south- been assessed systematically. The International Indian wards to ~30°S (ASCLME/SWIOFP 2012a, ASCLME/ Ocean Expedition (IIOE) of 1959–1965 collected infor- SWIOFP 2012b). mation on a broad range of subjects, including taxonomy, but the coverage of the WIO was patchy. Information on Elasmobranchs the megafauna named above is reasonably complete due Less than 200 elasmobranch species have been recorded to global interest in the species, and many are wide-rang- in the WIO and, except for South Africa, little effort has ing. However, limited sampling of invertebrate and even been made to assess the status of sharks and rays in the fish species with a view to their biodiversity assessment at region. Some emblematic species have been the focus of all depths in the water column and on the deep sea floor attention, such as the whale shark (Rhyncodon typus), and renders systematic estimates impossible. there is now an increase in interest in open ocean sharks Recent surveys by the MESOBIO and ASCLME pro- under the auspices of the Indian Ocean Tuna Commis- grammes have nevertheless resulted in significant addi- sion (IOTC) and its Working Party on Ecosystems and tions to our knowledge. ASCLME cruises covered parts Bycatch (WPEB). The most abundant pelagic shark fami- of the Mozambique Channel and Seychelles Basin, and lies in the South West Indian Ocean (SWIO) are the Lam- west of the Mascarene Plateau (see reports at www. nidae, Carcharhinidae and Alopiidae ASCLME/SWIOFP asclme.org), while the MESOBIO programme focused on 2012a, ASCLME/SWIOFP 2012b). Among the Lamni- the Mozambique Channel (Ternon and others, 2014). dae, great white sharks are mostly confined to southern However, in both cases, the bulk of work was on oceano- Africa but occasionally make incursions into tropical graphic and ecosystem processes, not diversity and tax- waters and are caught occasionally off most countries. onomy. Nevertheless, Huggett (2014) quantified the abundance of zooplankton species in the Mozambique Bony fish Channel from four cruises undertaken in 2007-2010, but While fish are among the best known of marine taxa, and did not attempt to estimate the proportion of biodiversity some 2 200 species are reported from the WIO (Smith identified or assessed. ASCLME cruises collected voucher and Heemstra 1986, Nelson 2006), a tally of those present specimens of fish, zooplankton and jellyfish, as well as tis- in the open ocean or deep sea has not been made and sue specimens for later DNA analysis.

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TRENDS AND THREATS areas, which may have cascading effects in offshore and deep waters; b) the introduction of invasive alien species. Future trends and threats to the deep sea and pelagic envi- The emerging threat of deep sea mining was not included ronments were most recently and comprehensively cov- in the assessment (eg minerals on the seabed), neither ered in the ASCLME/SWIOFP TDA (2012) and are were other extractive industries (eg for oil and gas), which discussed below within the DPSIR framework. can have severe impacts on surrounding habitats through physical alteration and/or pollution. Drivers Declines in living marine resources, including sharks The TDA identified ten root causes (or drivers) of change, and rays, pelagic and bottom fish, and excessive bycatch all of them applicable to threats to deep sea and offshore and discards as a result of expansion in artisanal, areas: inappropriate governance, economic drivers, inade- national and trans-national operations. Of twelve fish listed quate financial resources, inadequate knowledge and as threatened (ASCLME/SWIOFP 2012a, ASCLME/SWI- awareness, cultural traditions, population pressure and OFP 2012b) three are deep sea or open ocean species - the demographics, poverty and inequality, climate change and coelacanth (Critically Endangered), southern bluefin tuna natural processes, and personal attitudes (Thunnus maccoyii, Critically Endangered) and the big eye Of particular importance for the open ocean, which tuna (Thunnus obesus, Vulnerable). At present, marine mam- remains the last frontier for intensive human activity, are mal mortality through fisheries interactions in the SWIO, the following consequences of growing human populations while not exhaustively studied, are generally low and cer- and the attendant increase in pressures. tainly lower than in many other regions of the world. • Globalization of markets and trade, with the open Expansion in mariculture and associated consequences in ocean providing the main transport and shipping channels. terms of biosecurity, the introduction of diseases to wild For example, 30 per cent of global tanker traffic passes stocks, invasive species, habitat implications, and water through the Mozambique Channel, transporting oil from quality were noted. While mariculture occurs mainly in the Middle East to Atlantic markets, the tankers being too shallow waters, impacts to connected deeper waters and to large to pass through the Suez Canal. the seabed are possible. • Climate change and ocean acidification impacts on • Unpredictable environmental variability and marine environments are becoming increasingly well extreme events, including climate hazards and extreme known, these being driven by rising concentrations of weather events: a) ocean acidification, b) changes in sea- greenhouse gases in the atmosphere. Carbon dioxide has water temperatures, c) changes to hydrodynamics and the greatest impact on ocean chemistry as it affects the ocean circulation, d) changes in productivity (shifts in pri- buffering system in seawater, resulting in acidification and mary and secondary production) and e) geo-hazards, changes to the biochemistry of marine life. which in the deep sea may include volcanic eruptions and earthquakes. Pressures, state and impacts The TDA finally identified a number of emerging Four ‘main areas of concern’ are summarised here, combin- issues that may intensify and become significant threats in ing information on pressures, state and impacts through the future, including noise pollution, radioactive contami- causal chain analysis, providing guidance on needs at the nation and bio-prospecting. Prospecting for hydrocarbons both national and transboundary level. and minerals, particularly for the former in the Mozam- • Water quality: a) alteration of natural river flow and bique Channel in the immediate future, and further afield changes in freshwater input and sediment load, b) degrada- in future decades, will become major pressures on these tion of ground and surface water quality, c) microbiological presently unexploited resources. contamination from land-based and marine sources, d) solid wastes and from shipping and land- Responses based sources and e) oil spills from drilling, exploitation, Countries of the WIO are hampered from action in the transport, processing, storage and shipping. open ocean and deep sea by a lack of resources to manage • Habitat and community modification: a) a broad remote expanses of sea beyond their immediate coastlines. range of habitat disturbances in watershed and nearshore Nevertheless, almost the entire region recognized as the

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WIO is within the Exclusive Economic Zones of its mem- Global Oceans Biodiversity Initiative (GOBI). Scientific ber states, more so with the extension granted to Mauritius and technical experts have met to provide scientific and and Seychelles for the inclusion of the technical guidance on the use and further development in their continental shelf claims. Apart from South Africa, of biogeographic classification systems, and to identify , Mauritius and the Seychelles, other countries of sites which meet the criteria, including deep sea and open the region have few resources to actively manage the ocean sites (Table 1). This was accomplished in a work- waters under their jurisdiction. shop that focused on the Indian Ocean in July 2012 and Beyond territorial waters, responses by states of the its findings were accepted by the 12th Conference of Par- WIO to threats in the deep sea are dealt with under the ties of the CBD in Pyeongchang, South Korea, in October aegis of regional agencies mandated with resource extrac- 2014, laying a framework for marine spatial planning by tion and management (eg the Regional Manage- states in the region. ment Organizations, or RFMOs), the regional marine environmental protection convention arising from the Table 9.1. Ecologically and Biologically Significant Areas (EBSAs) described UNEP Regional Seas process (Nairobi Convention), or in the open ocean and deep seas of the Western Indian Ocean. Source CBD (2012). more bilateral actions (eg the seabed extension jointly sought by Mauritius and Seychelles). Other avenues to 1 Nursery Area reduce threats in the open sea such as the risk of pollution 2 Agulhas slope and seamounts 3 Offshore of Port Elizabeth and oils spills, include the ‘Marine Highway Project’ (GEF- 4 Protea Banks and sardine route WIOMHD 2012). 5 Natal Bight The generation and provision of information on deep 7 Delagoa shelf edge, canyons and slope sea and offshore ecosystems is increasing, building on the 9 Morrumbene to Zavora bay (Southern Mozambique) recent round of regional projects such as the ASCLME and 19 Mozambique Channel SWIOFP. These and other projects have compiled existing 22 Walters Shoal knowledge and conducted fresh research that is being dis- 23 Coral Seamount and fracture zone feature seminated through online portals and information 24 Northern Mozambique Channel resources, such as the Africa Marine Atlas (www.african- 26 Prince Edward Islands , Del Cano Rise and Crozet Islands marineatlas.org) supported by UNESCO and the Nairobi 27 Southern Madagascar (Part of Mozambique Channel) Convention Clearing House Mechanism, supported by 28 UNEP/Nairobi Convention Secretariat (2009). Linking 29 Mahe, Alphonse and Amirantes Plateau these portals with global resources, such as the Ocean Bio- 30 Atlantis Seamount geographic Information System (OBIS) is underway, and 32 Saya de Malha Bank will do much to fill the information gaps noted here. New Areas mentioned, but not assessed due to lack of information: regional programmes, such as the SAPPHIRE and SWI- 1 Coco de Mer (north Seychelles) 2 North Seychelles Oceanic Basin OFish programmes that will succeed those aforemen- 4 Saint Brandon* tioned, will include major components on biodiversity data 6 Dragon Vent Field, SW Indian Ridge and information systems in support of this process. In terms of on-the-ground interventions, there are several global conventions that include mechanisms to The UN Food and Agricultural Organization (FAO) protect marine waters, summarised below. A process to has noted the importance of identifying Vulnerable Marine clearly identify Ecological and Biologically Significant Ecosystems (VMEs) to promote the sustainability of fish- Areas (EBSAs) has been underway under the umbrella of eries worldwide (FAO 2009). The agency established the Convention on Biological Diversity (CBD). As in standards and prepared International Guidelines for VMEs other processes, marine ecosystems, and particularly the and, in July 2012, held a workshop in Mauritius to intro- open oceans and deep seas – termed Areas Beyond duce the concept of VMEs to WIO countries (FAO 2013). National Jurisdiction (ABNJ) or the High Seas – have VME standards have been formulated at the global level been among the last to be considered. Since 2007, a pro- for both national waters and areas beyond national jurisdic- cess has been convened to rectify this, assisted by the tion (ABNJs), as well as for deep sea areas vulnerable to

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BOX 9.1. COELACANTHS IN THE WIO by Matt Richmond and David Obura

A coelacanth and technical diver in the iSimangaliso Wetland Park, South Africa. © L. Ballesta.

Coelacanths (Latimeria chalumnae) are unique fish that sur- with single catch records in Mozambique and Kenya. They prised the world when discovered alive in 1938 after they occur at depths between 40 m and 400 m. Their persistence in were thought to have become extinct along with the dino- the Mozambique Channel may be related to the age and sta- saurs. Coelacanths belong to a special division of bony fish bility of the coastline, going back over 100 my. Coelacanths (Subclass Sarcopterygii), characterised by their unique lobed have been studied using mixed gas diving, by submersible fins that are considered to be the origins of fleshy limbs in ver- and by Remotely Operated Vehicle (ROV). They are considered tebrates. They have a hollow fluid-filled notochord rather than rare fish and are globally IUCN Red-listed as critically endan- the hard spine of other fish or the cartilaginous backbone of gered. Each individual has a unique white spot pattern that sharks. They also have a distinct tail with a small epicaudal fin allows for recognition and monitoring. at its tip. Coelacanths live for up to 60 years, give birth to as many as 26 live young, and can attain 2 m in length (or 70 kg) Coelacanths are believed to be slow-growing and very vulner- with females growing larger than males. Apart from the WIO able to . With increasing numbers of fishers, and species, Latimeria chalumnae, a more restricted species is greater use of shark and deep gill nets, larger numbers of coe- found in , L. menadoensis. lacanth are being caught. For example, 37 specimens had been landed up to October 2010 in Tanga, , alone, In the WIO, coelacanths live in deep tropical and subtropical leading to the formation of the Tanga Coelacanth Marine Pro- waters in South Africa, Tanzania, Madagascar and Comoros, tected Area.

deep technologies. The most vulnerable ecosys- VMEs is to facilitate the adoption and implementation of tems are those that are both easily disturbed and very slow conservation and management measures by Regional Fish- to recover, or may never recover. The aim of identifying ery Management Organizations (RFMOs) and flag states of

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BOX 9.2. Oceanic connectivity by green turtles in the WIO by Jérôme Bourjea and Mayeul Dalleau

Tracks of green turtles from nesting to foraging grounds (left) and space utilization density during migration (right). Extracted from Bourjea and others (2013) and Dalleau (2013).

Sea turtles have migrated for millions of years between nesting tion with human activities, Ifremer and Kélonia, both based in sites and feeding grounds, sometimes swimming thousands of Reunion, finished in 2013 an ambitious satellite tagging project kilometers, passing through several countries and ecosystems, that started in 2009 to better understand the spatial dynamics and interacting with human activities along the way—some- and connectivity of SWIO marine turtle populations. The pro- times to their advantage but sometimes resulting in a prema- ject deployed 105 satellite tags on nesting green turtles at ture end of their lives’ journeys. So it is in the Southwest Indian Europa, Juan de Nova, , Glorieuses, Moheli, and Trome- Ocean (SWIO). This region hosts some of the most important lin (left map) and cooperated with Mozambique to gather green turtle (Chelonia mydas) nesting sites in the world, most of tracks from Vamizi Island. Results showed that tracked turtles which are isolated on remote islands (for example, at Europa did their migration in 21,4 ± 16,2 days and travelled an average [Îles Eparses, France], Aldabra and Cosmoledo [Seychelles], and of 1359 ± 832 km from nesting site to their foraging ground, Moheli [Union of the Comoros]). Nesting also occurs in signifi- crossing from 2 to 7 different EEZ. This dataset also allowed cant numbers along the coasts of East Africa and Madagascar, identifying 5 key foraging hotspots in the SWIO, 2 in Mozam- which are better known for their vast pastures where bique (Bazaruto and Quirimbas archipelagos), 2 in Madagascar green turtles graze. Mayotte (France), Grande Comoros, and (northwest and south) and one in Tanzania (Mafia area). Thirty- Mauritius also have noteworthy foraging areas adjacent to their five per cent of the final foraging grounds of tracked turtles shores. However, very little is known about the migratory path- were in Marine Protected Areas. ways that sea turtles ply between their nesting and feeding grounds—and even less is known about how they spend their To better estimate migratory corridors, a Movement-based Ker- time among the various countries in the SWIO. nel Density Estimation (MKDE) was used to characterize the space utilization density during the migration (right map). To shed light on regional migratory issues related to interac- Results allowed highlighting hotspots of migration at the oce-

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anic and coastal scales. Oceanic corridors are diffused all along that interaction between East African and Malagasy artisanal the Mozambique Channel and migrating individuals most fisheries and adults green turtles are very important in all the probably faced few threats from open sea fisheries, composed SWIO, and that coastal development due to the discovery of on purse-seiners and longliners that do not interact with adult Gas fields in the Mozambique Channel (ie in the Quirimbas green turtle. Coastal corridors are more interesting as they are area, Mozambique) is increasing, such results are of great very dense from the north of Mozambique to south Tanzania, importance for management issues, allowing to identify areas in Bazaruto and all along the west Malagasy coast. Knowing of priority for the conservation of this endangered species.

fishing vessels. CONCLUSION Furthermore, the designation of Particularly Sensi- tive Sea Area (PSSA) under the International Maritime Until recently, countries of the WIO have taken few Organization (IMO) may be of assistance, particularly in steps to fully use, or manage, open sea areas under their limiting impacts from maritime operations. However, this jurisdiction. However, with growing evidence of the lim- designation has not yet been applied in the WIO, though its to terrestrial resources, the oceans are being seen as a its value has been recognized (Guerreiro and others, final frontier to support economic development. Use of 2011). The provisions of the United Nations Convention these areas without their adequate protection and on the Law of the Sea (UNCLOS) are also relevant, as knowledge of the associated consequences could result they identify ‘Special Areas’ relative to their vulnerability in severe degradation of the open ocean resources. As to maritime pollution under MARPOL, and an ongoing countries begin to embrace a ‘Blue Economy’ for wealth process under UNCLOS to establish mechanisms for creation, ensuring the sustainability and protection of governance of Areas Under National Jurisdiction will deep sea assets that may support such growth will be make this increasingly relevant. essential.

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